Heat exchange methods and apparatus

Abstract

A vapor component of a gas mixture is separated by condensation and is recovered for further use. A solvent vapor mixed with inert gas is condensed in a multistage heat exchange system in a manner which utilizes a first refrigerant to condense a portion of the vapor in a first heat exchange device, a second refrigerant, typically cold inert gas, for condensing a further portion of the vapor in a second heat exchanger and a third heat exchange device wherein the liquid phase of the inert gas (i.e. cryogenic liquid) is supplied to provide a source of refrigeration. In this latter heat exchange device, the cryogenic liquid is introduced into a body of condensed vapor thereby chilling such condensed vapor and stirring the same to avoid freezing. Chilled, condensed vapor is removed from the latter heat exchange device and is returned as a reflux thereto to condense the vapor component of the gaseous mixture supplied thereto. A further portion of the chilled, condensed vapor is recirculated to the body of condensed vapor to assist the stirring of this body to avoid freezing of condensed vapor which is collected from the above heat exchange devices and is passed to a suitable storage facility.

What is claimed is: 
     
       1. A method of continuously condensing a vapor component of a gas mixture supplied to a reflux heat exchange device containing a body of the liquid phase of said vapor component comprising the steps of: introducing a flow of a cryogenic liquid, having a boiling point below the boiling point of said vapor component, directly into said liquid phase body thereby chilling said liquid phase and stirring the same to substantially preclude freezing of said liquid phase; and   removing said chilled liquid phase from said device and returning said removed chilled liquid phase as reflux to said device and into contact with said gas mixture to thereby condense said vapor component.   
     
     
       2. The method defined in claim 1 wherein said cryogenic liquid is vaporized upon introduction to said liquid phase to form a cold gas which rises in said device into contact with said gas mixture to promote additional condensation of said vapor component. 
     
     
       3. The method defined in claim 1 additionally comprising the step of recirculating a portion of said removed, chilled liquid phase into said body of said liquid phase to augment stirring of said body. 
     
     
       4. The method defined in claim 1 additionally comprising the steps of discharging an overhead gas stream from said reflux heat exchange device; sensing the temperature of said discharged gas stream; comparing the temperature of said discharged gas stream with a temperature corresponding to a predetermined equilibrium partial pressure of said vapor component; and controlling the flow rate of said cryogenic liquid stream into said device to establish a chilled, reflux liquid temperature which effects condensation of said vapor to an extent such that the difference between the temperature of said discharged gas stream and said temperature corresponding to said equilibrium partial pressure is minimized. 
     
     
       5. The method defined in claim 4 additionally comprising the steps of supplying said discharged gas stream as a refrigerating medium to a further heat exchange device; and supplying a gas mixture having a greater concentration of said vapor component than in the gas mixture supplied to said reflux heat exchange device to said further heat exchange device to condense at least a portion of said vapor component from the gas mixture supplied to said further heat exchange device. 
     
     
       6. The method defined in claim 5 wherein gas which is not condensed in said second heat exchange device is supplied to said reflux heat exchange device as said gas mixture. 
     
     
       7. The method defined in claim 5 additionally comprising the steps of removing a further flow of said condensed, chilled liquid phase from said reflux heat exchange device; and removing a flow of said condensed vapor component from said further heat exchange device; combining said flows; and pumping said combined flow to a suitable storage device. 
     
     
       8. The method defined in claim 7 additionally comprising the steps of sensing the level of said condensed vapor component in said further heat exchange device; and controlling the rate of pumping said combined flow to said storage device to maintain said liquid level within a predetermined range. 
     
     
       9. The method defined in claim 8 additionally comprising the step of spraying a portion of said pumped combined flow into said gas mixture prior to introducing said gas mixture into said further heat exchange device to cool said gas mixture and to increase the concentration of said vapor component to approximately saturation. 
     
     
       10. The method defined in claim 1 wherein said gas mixture is comprised of a solvent vapor, the vapor phase of said cryogenic liquid and a minor concentration of moisture. 
     
     
       11. The method defined in claim 1 wherein the step of returning reflux liquid phase to said heat exchange device comprises passing said reflux downwardly over a gas-liquid contact medium countercurrent to a flow of said gas mixture upwardly therethrough whereby said vapor component is condensed upon contact with said reflux liquid phase.